When the Virginia Museum of Fine Arts opened its original Beaux Arts building in 1936, few people had trouble finding their way down its grand hallway and into the flanking galleries.

So smoothly did they flow in and out of the orderly succession of spaces that no one then would have predicted that some day in the future — after nearly 75 years and four additions — many visitors would find themselves wandering around and complaining about being confused and lost.

No one then could have imagined, moreover, that — after several-fold increases in its original size — even a 380,000-square-foot structure would be too small for the museum's burgeoning permanent collection and the audience-building traveling exhibitions needed to keep it vital.

Certainly they would not have envisioned the $150 million solution, which opens at the Richmond museum this weekend after nearly a decade of planning, fund-raising and construction.

Named for patrons James W. and Frances G. McGlothlin, the 165,000-square-foot addition not only provides a badly needed infusion of raw space but also goes a long way toward taming the mishmash of tangled traffic patterns that tied up visitors in the previous building configuration.

It gives the museum a fresh new public face, too, inviting visitors and bypassers in through its eye-catching, glass-punctuated front and side facades instead of asking them to come around back to the rear door.

Wrapped up in all these sweeping changes is a bold statement of ambition in which the VMFA aims to remake itself into one of the country's Top 10 art museums.

"We had far too little space for the kind of museum we want to be — and the spaces we had did not interact well," Director Alex Nyerges says.

"But now we have a much larger, more seamless whole — a whole that you can easily, almost intuitively understand. This is nothing short of a spectacular transformation — and it goes well beyond the additional space you see in the new wing."

Shepherded by London-based American architect Rick Mather and his associate Peter Culley — who've won critical acclaim for their previous work on several of Great Britain's most venerable museums — the project focused as much on taming the VMFA's nagging circulation problems as on designing an addition to make it bigger.

Both men spent hours studying the awkward configuration that had grown up over time — and which not only led visitors into numerous dead ends but also frequently left them confused and stranded.

"The biggest problem was coherency — coherency in the function of the building, coherency in its relationship to the rest of the museum campus and coherency in its relationship to the city," Culley says.

"This is a building that has grown up organically in piecemeal fashion over time — and the pieces didn't communicate with each other."

Mather and Culley's solution was not just a new wing but one that provided a way to tie all of the museum's previous additions together. Its key component is a giant three-level atrium that unites the new part of the building with the old — and which is traversed by a series of five pedestrian bridges that connect the new galleries in the McGlothlin wing with the existing display halls.

Together, the atrium, bridges and corridors now form a kind of 3-D street grid in which visitor traffic flows much more rationally and smoothly than in recent years.

"We now have all these incredible sight lines — especially from the Marble Hall in the 1985 addition and the Tapestry Hall in the original building back to the new wing," says Mitchell Merling, Paul Mellon Curator and head of the museum's European art department.

"That really helps tie the museum and its galleries together."

All the extra space provided by the new wing has added to the VMFA's impact, too, enabling it to double the number of objects in its permanent exhibits.

That's meant brand new galleries for the museum's Pre-Colombian and Native American works, which were previously exiled in storage, plus expanding, doubling and even tripling the space used to display its other holdings.

"We have one of the country's best collections of American art. Our Indian and Himalayan collection is one of the three best in the world. We have the best collection of Art Nouveau and Art Deco outside Paris — and I haven't even started talking about our English silver and our Fabergé," Nyerges says.

"With this new wing, we'll finally be giving them the kind of space they deserve."

While space for the permanent collection has expanded by 50 percent, the changing exhibit galleries have doubled in size, enabling the museum to bring in large international traveling shows that it simply had no room for before.

Among the scheduled exhibits is a milestone collection of Tiffany glass and decorative arts that sparked huge crowds when it debuted in Paris earlier this year.

Similar shows are on the horizon, Nyerges says, noting that the state-supported VMFA generates an estimated $5 in jobs and tourism revenue for every dollar spent on its operations.

And many of those exhibits will be calculated to impress the museum world as well as new visitors.

"There is no exhibition that we can't accommodate now — and we'll be looking globally to bring great exhibits to Virginia," he says.

"This is the most important show of Tiffany that's ever been done — and the only place in America you'll be able to see it is right here."